广州旱季双高污染及消光系数垂直分布特征

High aerosol and high ozone pollution and vertical distribution of extinction coefficients in Guangzhou during the dry season

利用2017年12月6日~2018年1月3日地面常规气象资料、空气质量6参数、光化辐射资料、气溶胶吸收和散射系数、单次散射反照率、激光雷达反演的气溶胶消光系数与退偏比数据,分析广州地区气象参数变化对污染物浓度的影响和气溶胶对光化辐射的衰减,研究双高(高气溶胶与高O_(3))污染的形成机理,并从垂直角度探究了双高日边界层内消光系数廓线演变规律.结果表明,研究期间双高日对光化辐射的衰减小于霾日,一方面气溶胶的散射和吸收特性使得其对光化辐射具有一定的衰减作用,另一方面气溶胶中的散射性成分对光化辐射具有正反馈作用,双高日较强的光化辐射使得O_(3)和PM_(2.5)同时维持在较高值.与非双高日相比,双高日全天风速更小、温度更高、光化辐射更强,PM_(2.5)和CO、SO_(2)、NO_(2)等物质浓度更高,细粒子占比更大,11:00~16:00间近地面退偏比更高.雷达观测结果表明4个双高日8:00消光系数高值区在0.5km以下,低层出现消光系数均值区,并且均值区不断升高;午后光化辐射强度减弱,均值区不再向上发展,随着颗粒物污染加剧,均值区以上消光系数垂直递增,在边界层顶附近出现峰值;夜间消光系数在低层随高度升高而降低,某一高度范围消光系数随高度增加而升高,1km以上呈指数递减,夜间边界层顶附近高值区较为明显.

Based on regular surface observation meteorological data,data of six kinds of air quality parameters,actinic radiation data,aerosol scattering and absorption coefficients,single scattering albedo,and aerosol extinction coefficient and depolarization ratio retrieved by lidar data from December 6,2017 to January 3,2018 in Guangzhou,this paper analyzed the influence of meteorological parameters variation on pollutant concentration and actinic radiation attenuation by aerosols,studied the formation mechanism of high aerosol and high ozone(double high)pollution,and explored the evolution of extinction coefficient profile in the vertical direction within the boundary layer on double high days.The actinic radiation attenuation on double high days is less than that on haze days during the study period.The scattering and absorption of aerosols has certain attenuation effect on actinic radiation.The scattering components of aerosols have positive feedback on actinic radiation,and the strong actinic radiation on double high days keeps O_(3) and PM_(2.5) concentration at a high level.Compared with non-double high days,double high days feature lower wind speed,higher temperature,stronger actinic radiation,higher PM_(2.5),CO,SO_(2),and NO_(2) concentration,higher fine particle ratio,and higher near-surface depolarization ratio during 11:00-16:00.Radar observation shows that the high value area of extinction coefficient is below 0.5km at 8:00 am on four double high days.The mean value area of extinction coefficient appears in the low layer and keeps rising.Actinic radiation flux abates in the afternoon,and its mean value area no longer develops upwards.Extinction coefficient above the mean value area gradually increases vertically as particulate pollution aggravates,and it peaks near the top of the boundary layer.At night,extinction coefficient reduces with the rise of height at the low altitude,increases with the rise of height within a certain altitude range,and decreases exponentially above 1km.The high value area near the top of the boundary layer is more obvious at night.